Design of Maximum Power Point Tracker for Varying Load

Title Design of Maximum Power Point Tracker for Varying Load
Authors Rezwana Chowdhury, Maima Ahmed Preeti, Nigar Hossain
Semester Fall, 2016

MPPT (Maximum Power Point Tracker) is a device that aids a solar panel in its operation to track maximum power output under various external factors. This device ensures to increase the efficiency of power transfer from the solar panel to the load. Interestingly, power produced by photovoltaic cells is not stable under constant light intensity and temperature as each voltage output corresponds to a different power level unlike other sources of renewable energy. Every solar irradiation under constant temperature corresponds to a unique non-linear current versus voltage graph where only a particular voltage and its current yields the maximum power, known as Vmpp and Impp respectively.

Our project is to come up with an improved version of a MPPT algorithm and implement it to test with varying loads to accommodate different solar irradiation levels accompanied by temperature fluctuations using a panel capable of giving an optimum power output of 50W.

In order to meet our project goal, we have used fractional open circuit voltage method, an indirect way of calculating Vmpp (maximum power point voltage) which lies 20% less than Voc (open circuit voltage). This method yields more accurate results because it gives various Vmpp throughout the day in accordance to the varying solar irradiation levels when compared to fixed voltage method where a predetermined value of Vmpp is set in the code and irrespective of whatever the Voc is, the voltage would have been shifted to the designated value. The shifting of voltage is achieved by an IC which is better suited to handle PWM pulses from Arduino in comparison to a buck converter.

There were several resources available online to guide us in designing an efficient algorithm but no information was available which deals with the variation of load concept. Ability to boost up power transfer efficiency will help us to minimize the use of expensive batteries for storage and also avoid further power loss.